Coastcom D/I Mux III System User Manual page 207

Chapter 5. Diagnostics
Drop-and-Insert: T1-1 and T1-2 Line Loopback
Line Loop Set code received on span B input causes PCM to be looped back out span A's
output, as well as being passed on to the input of LIU B. The PCM from the output of the
LIU A is blocked. Line Loop Set code received on span A input causes PCM to be looped
back out span B's output, as well as being passed on to the input of LIU A. The PCM
from the output of LIU B is blocked, as illustrated in Figure 5-15.
Figure 5-15. Drop-and-Insert: T1-1 and T1-2 Line Loopback
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